Some existing toroidal worm grinding equipment have been developed recently, such as German HNC 35 TP and the Chinese Patent No. ZL92204765.0 patent entitled “Four-simultaneously-working-axis computerized numerical controlled toroidal worm grinding machines”. This equipment has such advantages that the thread of plane enveloping toroidal worms can accurately be formed in once grinding; the ground workpieces can acquire high accuracy and perfect surface roughness. However, their deficiencies are low productiveness and expensive machining cost, so that it results in very high cost of the machined workpieces and cannot meet the needs of constantly developing production.
The technical problem to be solved by this invention is to provide a sort of five-simultaneously-working-axis CNC tooth-cutting machine tools for accurately forming plane enveloping toroidal worms in order to improve the productivity and reduce the cost.
In order to solve the above technical problem the technical scheme adopted by this invention is to provide a five-simultaneously-working-axis computerized numerical controlled tooth-cutting machine tool for plane enveloping toroidal worms, comprising a body of the machine tool and a controlling cabinet. The body comprises a bed, a spindle box with a spindle, a longitudinal sliding table, a vertical guideway, a traverse slider and a tailstock, a cutter rest that supports a rotating cutter head is mounted on the vertical guideway, the spindle rotates about A-axis thereof, the table longitudinally slides along Y-axis relative-to the bed, the cutter head rotates about B-axis thereof and transversely shifts along X-axis, as well as the cutter head makes up of down shift along Z-axis of the vertical guideway. The controlling cabinet is equipped with programs for controlling the five axes of A, Y, X, Z and B to simultaneously work together, wherein a first coordinate system Σ1 is connected with the workpiece, a second coordinate system Σ2 is connected with an imaginary gear, a third coordinate system Σ3 is connected with the rotating cutter head and a four coordinate system Σ4 is connected with the cutting edges, based upon the operating transformation of the coordinate systems, the motion equations of the five axes of the machine tool are determined so that the shift of the cutting edges of the cutter on the cutter head is controlled to simulate an inclined plane in spatial locations in order to envelop cut the tooth flanks of plane enveloping toroidal worms.
Perfectly, the inclined plane simulated by the cutting edges of the cutters rotates around the central axis of the imaginary gear k2(o2), i.e. the composition of both the rotation of B-axis and the revolution of B-axis around the axis of k2(o2), at the same time the workpiece rotates around J1(o1) (i.e. A-axis), in the course of relative motions the tooth flank of plane enveloping toroidal worm is generated.
Perfectly, the tooth forming motion of plane enveloping toroidal worm can correctly be controlled by means of controlling the values of a rotating angle φ, of the workpiece rotating around j1(o1)-axis, a rotating angle φ2 of the imaginary gear rotating around k2 (o2)-axis, a rotating angle φ, of the cutter head rotating around k3 (o3)-axis, the included angle τ between the radius vector r and the coordinate axis j2(o2) while the center o3 of the cutter head rotating around the center o2 of the imaginary gear and a distance h of the center o2 of the imaginary gear making straight-line shift along thereof central axis k2 (o2)-axis to point o5, in which φ1/φ2 is equal to the gear ratio between the machined worm and the imaginary gear.
Perfectly, there are at least two blades mounted on the rotating cutter head, the cutting edges of the blades are of straight line which lies on the plane perpendicular to the axis of the rotating cutter head.
Perfectly, the cutter edges are all located on two tooth planes of the imaginary gear; while two tooth planes are inclined with an angle β with respect to the central axis of the imaginary, gear and tangential to two imaginary spatial cones respectively; the half conic angles of two cones are equal to the inclined angle β, the radius rb of said imaginary cones is equal to the radius rbt of the main basic circle of the imaginary gear, the cutting edges on the cutter head shift along the tooth plane imaginary gear; while the inclined plane is tangential to the spatial cone and rotates around the central axis k2(o2) of the cone; the center o2 of the imaginary gear makes up or down shift along the vertical axis k2(φ2), the cutting edge comes into cutting at point N and secedes from cutting at point S, the coordinates of every point on the workpiece make following-up motions along X-, Y-and Z-axes while B-axis, makes the circular-arc interpolating motion around the central axis k2(o2) of the imaginary gear. In other words, the resultant motion of shifts along X-, and Y-axes, is equivalent to the revolution of B-axis around the central axis k2(o2) of the imaginary gear.
Perfectly, the spindle box and the tailstock are fixed on the longitudinal sliding table that is movably mounted on the bed, and the traverse slider is mounted on the bed.
The effect of the machine tool is that the rotating speed of cutter shaft and workpiece shaft can make the cutting velocity up to 200 m/min, thus the working efficiency is six to seven times higher than that of worm grinding and the productivity can greatly be improved. The machine tool of the present invention is to supplement the deficiency of toroidal worm grinding machines and to provide a sort of high-productivity tooth cutting machine tools.